Acquisition Protocol. All SPECT studies are performed with parallel hole collimators and gated acquisitions protocol (10% RR window) acquired into 16 time bins. Data Processing of Gated data sets are assessed for mean counts, corrected for dose, decay and time of imaging, are measured in each segment utilizing 4D-MSPECT (INVIA, Ann Arbor, Michigan). MPI is defined as the corrected stress counts divided by corrected rest counts.